As air travel has increased over the past decades, airport facilities have become more crowded and congested. Minimizing the time between the arrival of an aircraft and its departure to maintain an airline's flight schedule, and also to make a gate or parking location available without delay to an incoming aircraft, has become a high priority in the management of airport ground operations. The safe and efficient ground movement of a large number of aircraft simultaneously into and out of ramp and gates areas has become increasingly important. As airline fuel costs and safety concerns and regulations have increased, the airline industry is beginning to acknowledge that continuing to use an aircraft's main engines to move aircraft during ground operations is no longer the best option. The delays, costs, and other challenges to timely and efficient aircraft pushback from airport terminals associated with the use of tugs and tow vehicles makes this type of aircraft ground movement an unattractive alternative to the use of an aircraft's main engines to move an aircraft on the ground. Restricted use of an aircraft's engines on low power during arrival at or departure from a gate is an additional, although problematic, option. Not only does such engine use consume fuel, it is also burns fuel inefficiently and produces engine exhaust that contains microparticles and other products of incomplete combustion. Operating aircraft engines, moreover, are noisy, and the associated safety hazards of jet blast and engine ingestion in congested gate and ramp areas are significant concerns that cannot be overlooked.
The use of a drive means, such as an electric motor, mounted with an aircraft wheel to rotate the wheel of an aircraft to drive the aircraft on the ground without using the aircraft's main engines has been proposed. Various drive means and motors intended to drive aircraft during ground operations are described in the art. For example, an aircraft electric taxi system with a friction-actuated bi-directional clutch mounted with a gear system and the aircraft's brakes on main landing gear wheels is described in U.S. Patent Application Publication No. US2012/0126053 to Christensen et al. The owner and inventors of the present invention have, in addition, developed and implemented an aircraft drive system that uses electric drive motors to power aircraft nose or main landing gear wheels to effectively move an aircraft autonomously during ground operations without reliance on the aircraft's main engines or external vehicles. The prior art, however, does not suggest an aircraft drive wheel drive mechanism with a clutch-activated drive system that actuates electric drive means to selectively produce a braking torque on a drive wheel as the drive wheel, and the aircraft, are moved by the drive mechanism only in a reverse direction.
The drive means currently proposed to drive aircraft on the ground typically rely on gearing systems that operate with the drive means to drive an aircraft wheel and, thus, the aircraft. Traction drives, such as that described in U.S. Pat. No. 4,617,838 to Anderson, available from Nastec, Inc. of Cleveland, Ohio, which relies on ball bearings, can be used to replace gears in some contexts. Adapting roller or traction drive systems to replace gearing and/or gear systems in an aircraft drive wheel to actuate drive means that independently drive an aircraft drive wheel has not been suggested, nor has the use of a clutch assembly specifically designed to controllably activate such roller traction drive systems or drive means to selectively produce drive means braking torque been mentioned.
Many types of vehicle clutch assemblies are well known in the art. U.S. Pat. No. 3,075,623 to Lund; U.S. Pat. No. 3,599,767 to Soderquist; and U.S. Pat. No. 7,661,329 to Cali et al, for example, describe clutch assemblies incorporating sprag or pawl elements that may transmit torque between races or rotatable elements depending, in part, on their relative directions of rotation. Neither these clutch designs nor other commonly available clutch designs are sufficiently robust to function effectively and reliably in an aircraft drive wheel system to controllably engage a drive system and selectively actuate a drive means as required to operate as a brake only when needed, such as when an aircraft is driven autonomously in reverse during ground operations.
A need exists, therefore, for an effective and reliable clutch assembly specifically designed to selectively engage an aircraft drive wheel drive system with a highly efficient drive system-actuated drive means that drives an aircraft drive wheel to move the aircraft autonomously on the ground without reliance on the aircraft's main engines or external ground vehicles. A need particularly exists for such a clutch assembly that is specifically designed to selectively provide braking torque to the drive system-actuated drive means to permit or prevent operation of the drive means as a brake.